Perch Dying in Native UK Aquarium: Cloudy Eyes

150-gal native tank: chub, carp, bream, tench, red-finned perch. Perch dying with cloudy eyes, spreads. Treated, clears, returns. Water "fine" (API master kit, 5 params). One healthy, one sick in nurse tank.

Cloudy Eyes = Generic Stress Symptom

Not a specific disease. Causes: high GH (general hardness), poor water quality, parasites, bacteria, bullying.

Missing Test: General Hardness (GH)

High GH weakens immune system over time, causes cloudy eyes. API master kit may not include GH.

Checklist

• Test GH.
• Check for clamped fins, flashing, tumors, red streaks, lethargy, appetite change, gasping, hard/slime-less feel.
• Verify test kits not expired.

Perch are sensitive. GH often overlooked. Test it.